Antenna coupling system



Dec. 27, 1938. H. VOG-r 2,141,573

ANTENNA COUPLI'NG SYS TM Filed July 11, 1935 Patented Dec. 27, 1938 UNITED STATES ANTENNA COUPLING SYSTEM Hans Vogt, Berlin-Lichterfelde, Germany, assignor to Ferrocart Corporation of America, New York, N. Y., a corporation of Delaware Application July 11, 1935, Serial No. 30,905 In Germany July 18, 1934 11 Claims.

In the high frequency coils predominantly used in recent times, possessing a magnetic core, giving small losses, consisting of small magnetic particles and an insulating binder, the coupling windings, which serve as aerial coupling and reaction coupling, have previously been wound in xed relation to the oscillatory circuit Winding.

This arrangement had various disadvantages. With given single self-inductances L1 of the oscillatory circuit coil and L2 of the antenna coupling coil, the coupling ratio K or the mutual inductance M was automatically fixed at a delinite value. However, the technical task is often imposed of giving the three factors, L1, L2, and M particular magnitudes independent of each other. In addition, owing to the coupling winding, the space required by the oscillatory circuit coil was unnecessarily increased, and thus the magnetic path, which must be made as short as possible in order to achieve small losses, was lengthened. As the result of the close proximity of the oscillatory circuit coil to the coupling windings, there was produced a considerable increase of attenuation in the oscillatory circuit coil. Variable coupling was mechanically impossible of achievement with the previous arrangement.

It has also been proposed to form interstage coupling transformers by arranging coils on rod or bar type magnetic cores, the axes of the cores and coils of the transformer windings being normal to each other. These arrangements have the disadvantage that the magnetic eld extends to a substantial distance beyond each coil assembly, and shield cans of relatively large size were required. c

The present invention eliminates all of these disadvantages, improves the electrical characteristics and provides an economical mechanical construction. In accordance with the invention, the coupling windings are fitted in a separate space from the oscillatory circuit winding, in such a Way that they do rnot lie in the main magnetic eld of the oscillatory circuit coil, but in the leakage ilux, flowing outwards, of the latter. This is made possible by locating the coupling windings outside the magnetic flux circuit iormed by a closed, or approximately closed, magnetic core. In this way considerable advantages are obtained. The space required ior the oscillatory circuit coil is decreased to the extent of the space required for the coupling windings, so that the path of the magnetic flux owing around the oscillatory circuit winding is correspondingly shortened. In this way the losses are naturally lessened, all the more so because at the same time the coupling windings are removed from the immediate neighborhood of the oscillatory circuit winding.

In addition it is possible, in this way, to comply (Cl. Z50-20) with the requirement imposed in the building of wireless receiving sets, of xing the three magnitudes-self-inductance of the oscillatory circuit winding L1, a self-inductance of the coupling winding Lz, and the mutual inductance M-independently of each other. In particular, however, it becomes possible to make the coupling factor K variable, by making the coupling winding movable. In addition, it is possible to move an additional magnetic body at the same time as the coupling winding, which magnetic body is of such a nature and so arranged that the alteration of the self-inductance of the oscillatory circuit coil, produced by the movement of the coupling winding, is compensated thereby. In this way an appreciable shortcoming adhering to such arrangements with variable coupling up to the present time, is eliminated.

In special cases it is possible, in particular for the above-mentioned purpose of compensating the self-inductance, to fit the coupling windings also on an entirely separate magnetic core, which gives rise to particular advantages.

A few examples of construction will now be described with the aid of the illustrations, While it is however to be stressed that the new arrangement can also be applied in other Ways.

In the accompanying drawing, Figs. l, 2 and 3 are longitudinal central sections through difierent forms of coupled inductances, and Figs. 4 and 5 are schematic circuit diagrams of antenna coupling systems that include coupled inductances such as shown in Fig. 1.

Fig. 1 shows a high frequency coil, which consists of a bar core l, two magnetic discs 2 tted thereon, an oscillatory circuit winding 3 lying between the magnetic discs' 2 and coupling windings 4 and 5. The magnetic core parts consist preferably of a mixture of magnetic powder and an insulating binder with a permeability (fixed and calculated at the circular core) of about 5-20. The windings are preferably in the form of self-supporting windings or mechanically rigid units with the aid of a coil frame. The magnetic flux of the oscillatory circuit coil traverses, as shown by the dotted lines, the bar core, the discs and the air gap. The magnetic circuit however can be closed by a jacket of the same magnetic material if required t-o reduce the stray field. The coupling windings 4 and 5 represent the aerial coupling and the reaction coupling, or else both are connected in series and work as a twopart antenna coil, while the reaction coupling is tted together with the oscillatory circuit coil. The coils 4 and 5 lie outside the4 main magnetic flux of the oscillatory circuit winding, so that the coupling is effected only by the leakage field of the main winding 3 or the coupling windings 4 and 5. Thus, according to the number of windings and the proximity of the coupling windings, L1, L2 and M can be varied within wide limits. By moving backwards and forwards the coils i and 5, the coupling can be made variable, while the seli-inductance of the main coil can be varied by moving the discs 2, or by division of the bar core i into two halves with variable air-gap between them. If an additional magnetic body oi a suitable nature is arranged in a suitable position, this being mechanically joined to the movable coupling windings, then it is possible to balance, at least approximately, the alteration or the seli-inductanee of the oscillatory circuit winding consequent upon the movement of the coupling windings. Such an example of construction is shown in Fig. 2.

Fig. 2 depicts the arrangement of a movable coupling coil with a compensating magnetic body. The oscillatory circuit coil I2 with the self-inductance L1 is mounted on the coil frame i3, of material giving small losses, which is iitted on a magnetic core, which can consist of one piece or, advantageously, of three parts I4, I5, I6. The coupling coil I with the self-inductance L2 is mounted on-the coil frame I8, made of material giving small losses, which is iitted on the special compensating core, also preferably consisting of two parts I9, 20. By moving the compensating core with the coil I'I mounted on it, the coupling factor lc is changed. The increase of self-inductance of the coil L1, consequent upon the moving away of the coil L2, or the decrease of self-inductance of the coil L1 consequent upon the approaching of the coil L2, is balanced by the magnetic body I9, 2U which is moved at the same time.

The last arrangement in particular will be used with great advantage in wireless receiving sets, because it makes possible, by simple means, a variable coupling, eliminating additional coupling members, such as variometers, coupling condensers or the like, and also makes possible the alteration of coupling without eiect on the tuning.

Fig. 3 shows a somewhat different arrangement. The magnetic core consists here of two bowl-shaped halves 6 and '1, a coil frame of insulating material 8, this material giving small losses, the oscillatory circuit winding 9, a further coil frame I, and the coupling winding mounted thereon, II. Here again the magnetic flux flows, for the most part, in the magnetic path formed by the magnetic core, as shown by the dotted lines. The coupling between the coils 9 and I I depends upon the length of the air gap 2l which is provided between the annular rims or anges of the cup-shaped members 6 and 'I surrounding the winding 9.

Typical antenna coupling circuits employing the inductances of Fig, l are shown in Figs. 4 and 5. As shown in Fig. 4, inductance Lz is connected between the antenna and ground, inductance L1 is shunted by a tuning condenser C and connected to the input terminals of the tube T, and induotance L3 is connected as a feedback coil. The coupling between the antenna coil L2 and the oscillatory circuit coil L1 is indicated by the bracket and character M, and the feedback coupling is indicated by the bracket and character M1. In the Fig. 5 circuit, the coils L2 and La are serially connected in the antenna circuit and coupled to the oscillatory circuit coil L1.

I claim:

l. In an antenna coupling system, the combination with an oscillatory circuit coil, a conderser for tuning said coil to resonance at a high frequency, and magnetic core means including a section extending into the coil and a section extending across an end of said coil, of an antenna circuit coupling coil substantially coaxial with said oscillatory circuit coil in the leakage iield of said magnetic core means, said coupling coil being separated from said oscillatory circuit coil by the end section of said magnetic core means.

2. In an antenna coupling system, the combination with an oscillatory circuit coil, a condenser for tuning said coil to resonance at a high frequency, and magnetic core means including a central section extending into said coil and end sections at and extending across the opposite ends of said coil, of an antenna circuit coupling coil coaxial with said oscillatory circuit coil and located outside of the space defined by said end sections in the leakage field of said magnetic core means.

3. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means extends through said oscillatory circuit coil and projects beyond said end sections, and said coupling coil is positioned around said central section.

4. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means extends through said oscillatory circuit coil and projects beyond said end sections, and said coupling coil is positioned around and slidably mounted on said central section.

5. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means has end anges constituting said end sections.

6. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means has end anges constituting said end sections, and said coupling coil has a separate magnetic core spaced from the magnetic core means of said oscillatory circuit coil.

7. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means has integral end anges constituting said end sections, said end anges terminating in circumferential portions extending towards each other and partially enclosing said oscillatory circuit coil.

8. Apparatus as claimed in claim 2, wherein said central section of the magnetic core means has end anges constituting said end sections, and said coupling coil is carried on a coil support slidable upon the end flanges of said magnetic core means.

9. An antenna coupling system for a radio receiver comprising an oscillatory circuit coil, a condenser for tuning said coil to the frequency of a desired radio signal, an approximately closed magnetic core means for said coil, and an untuned antenna coil in the leakage field of said oscillatory circuit coil and separated therefrom by a portion of said magnetic core means.

l0. An antenna coupling system as claimed in claim 9, wherein said coils are coaxial, and said magnetic core means includes a section within said oscillatory circuit coil and an end section positioned between the two coils.

ll. An antenna coupling system as claimed in claim 9, wherein said coils are coaxial, and said magnetic core system includes a section extending into said oscillatory circuit coil 4and an integral end flange positioned between the two coils.

HANS VOGT. 

